Two novel copper carboxyly-phosphonates, namely, Cu_2.5(5-pnc)(SO₄)_0.5(OH)(H₂O)_0.5 (1) and Cu_0.5(5-pncH₂)(H₂O)_1.5 (2) (5-pncH₃ = 5-phosphono-1-naphthalenecarboxylic acid), have been synthesized and characterized by X-ray diffraction, infrared spectroscopy, elemental analysis, and thermogravimetric analysis. In compound 1, each {PO₃C} tetrahedron is corner-shared with two {Cu(1)O₄}, two {Cu(2)O₅} and one {Cu(3)O₅}, thus forming a one-dimensional inorganic chain along the c axis containing 8-membered rings of [Cu₃O₄S] and 19-membered cages of [Cu₅O₁₀P₄]. The inorganic chains are further connected by a 5-pnc^3- ligand to generate a three-dimensional framework. Compound 2 exhibits a one-dimensional structure, in which the inorganic chains of [Cu-O-Cu]_n are connected by the organic ligands through hydrogen bonding interactions, forming an infinite two-dimensional layer. Magnetic measurements of 1 indicate that dominant antiferromagnetic interactions are mediated between the Cu²⁺ centers.